Deep sleep and “brain cleaning”: what the glymphatic system is and why it matters for memory

Every morning, after a night of restful sleep, most of us notice the same thing: we think more clearly, concentrate more easily and feel more energetic.

For a long time, researchers considered sleep to be mainly a period of rest for the brain. Discoveries in recent decades, however, have changed this view. Today we know that complex processes essential for brain health take place during sleep.

One of these discoveries is the glymphatic system, a specialised mechanism involved in clearing waste products that build up in the brain over the course of the day.

Does the brain produce “waste”?

Although the term may seem surprising, the answer is yes.

The brain is one of the most active organs in the body. Billions of neurons are constantly communicating, using energy and generating metabolic products that need to be cleared efficiently.

Just as a city produces waste every day that has to be collected and taken away, the brain also needs a system to remove the substances produced by its continuous activity.

The discovery of the glymphatic system

In 2012, researchers described a mechanism that works as a drainage system for the brain.

It was named the glymphatic system, and it uses the circulation of cerebrospinal fluid to help clear waste products from between nerve cells.

Studies, mostly in animals, suggest that this system becomes much more active during deep sleep, which is what caught the scientific community’s attention.

What happens during deep sleep?

The brain stays active: fluid flows are reorganised in a way that seems to let some substances accumulated during the day be cleared more efficiently.

These include proteins that have been studied intensively in connection with Alzheimer’s disease.

This discovery has opened up new lines of research into the relationship between sleep, memory and long-term cognitive health.

Sleep and brain health

Current research suggests that chronic sleep disorders may influence biological processes that are important for brain function.

This does not mean that one sleepless night will have major effects, or that insomnia automatically leads to a neurodegenerative disease.

Even so, sleep quality is now seen as one of the factors that help keep the brain healthy throughout life.

What can we do for better sleep?

A few simple habits can support good-quality sleep:

• keeping a regular sleep schedule;
• getting natural light in the first part of the day;
• less screen time before bed;
• regular physical activity;
• limiting alcohol in the hours before bed;
• a quiet, comfortable place to rest.

When to talk to a doctor

If your sleep has been unrefreshing for some time or tiredness is affecting your daytime activities, talk to a doctor. An assessment can show what lies behind the problem: sometimes a habit, sometimes anxiety, depression or another condition.